A Novel Class of Oxylipins,sn1-O-(12-Oxophytodienoyl)-sn2-O-(hexadecatrienoyl)-monogalactosyl Diglyceride, fromArabidopsis thaliana

Boguslawa A. Stelmach, Axel Müller, Peter Hennig, Steffen Gebhardt, Manfred Schubert-Zsilavecz, Elmar W. Weiler
2001 Journal of Biological Chemistry  
The cyclic derivative of 13(S)-hydroperoxolinolenic acid, 12-oxophytodienoic acid, serves as a signal transducer in higher plants, mediating mechanotransductory processes and plant defenses against a variety of pathogens, and also serves as a precursor for the biosynthesis of jasmonic acid, a mediator of plant herbivore defense. Biosynthesis of 12-oxophytodienoic acid from ␣-linolenic acid occurs in plastids, mainly in chloroplasts, and is thought to start with free linolenic acid liberated
more » ... membrane lipids by lipase action. In Arabidopsis thaliana, the glycerolipid fraction contains esterified 12oxophytodienoic acid, which can be released enzymatically by sn1-specific, but not by sn2-specific, lipases. The 12-oxophytodienoyl glycerolipid fraction was isolated, purified, and characterized. Enzymatic, mass spectrometric, and NMR spectroscopic data allowed us to establish the structure of the novel oxylipin as sn1-O-(12-oxophytodienoyl)-sn2-O-(hexadecatrienoyl)-monogalactosyl diglyceride. The novel class of lipids is localized in plastids. Purified monogalactosyl diglyceride was not converted to the sn1-(12-oxophytodienoyl) derivative by the combined action of (soybean) lipoxygenase and (A. thaliana) allene oxide synthase, an enzyme ensemble that converts free ␣-linolenic acid to free 12-oxophytodienoic acid. When leaves were wounded, a significant and transient increase in the level of (12-oxophytodienoyl)-monogalactosyl diglyceride was observed. In A. thaliana, the major fraction of 12-oxophytodienoic acid occurs esterified at the sn1 position of the plastid-specific glycerolipid, monogalactosyl diglyceride.
doi:10.1074/jbc.m010743200 pmid:11278736 fatcat:zo2kijuzyzepzlg2eyxzhqytyy